Guinea forward Bangoura, 28, had signed a four-year deal in the United Arab Emirates in September 2010 after falling out of favour at Rennes, and Al-Nasr had argued Nantes had "incited the player to wrongly break his contract".

The ruling means Nantes, who currently lead Ligue 2 and are well on course to return to Ligue 1 for the first time since 2009, will have to sit on the sidelines during this summer's transfer window, and the following one in January 2014. However, they are to launch an appeal, which should allow them to continue to wheel-and-deal until the process is completed.

"We are, of course, going to appeal," Nantes president Waldemar Kita told Presse-Ocean. "We have 21 days to do that. We're facing two or three years of war." Kita added that, during that period, Nantes "will be able to do what we want, i.e. recruit players".

"Ismael Bangoura had not been paid for several months and had been 'un-registered' by his club. So, he was out-of-contract," the Nantes chief said.

Bangoura, who is currently on loan at Qatari club Umm Salal, was banned from competitive football for four months. The former Dynamo Kiev forward and Nantes were also ordered to pay Al-Nasr a total of €4.5 million.